Fuel cell power systems and methods of controlling a fuel cell power system

ABSTRACT

Fuel cell power systems and methods of controlling a fuel cell power system are provided. According to one aspect, a fuel cell power system includes a plurality of fuel cells electrically coupled with plural terminals and individually configured to convert chemical energy into electricity; and a digital control system configured to at least one of control and monitor an operation of the fuel cells. Another aspect provides a method of controlling a fuel cell power system including providing a plurality of fuel cells individually configured to convert chemical energy into electricity; electrically coupling the plurality of fuel cells; providing a first terminal coupled with the fuel cells; providing a second terminal coupled with the fuel cells; and coupling a digital control system with the fuel cells to at least one of monitor and control an operation of the fuel cells.

RELATED PATENT DATA

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/108,667, filed on Jul. 1, 1998, which was acontinuation-in-part of U.S. patent application Ser. No. 08/979,853,filed on Nov. 20, 1997.

TECHNICAL FIELD

[0002] The present invention relates to fuel cell power systems andmethods of controlling a fuel cell power system.

BACKGROUND OF THE INVENTION

[0003] Fuel cells are known in the art. The fuel cell is anelectrochemical device which reacts hydrogen, and oxygen, which isusually supplied from the ambient air, to produce electricity and water.The basic process is highly efficient and fuel cells fueled directly byhydrogen are substantially pollution free. Further, since fuel cells canbe assembled into stacks of various sizes, power systems have beendeveloped to produce a wide range of electrical power output levels andthus can be employed in numerous industrial applications.

[0004] Although the fundamental electrochemical processes involved inall fuel cells are well understood, engineering solutions have provedelusive for making certain fuel cell types reliable, and for otherseconomical. In the case of polymer electrolyte membrane (PEM) fuel cellpower systems reliability has not been the driving concern to date, butrather the installed cost per watt of generation capacity has. In orderto further lower the PEM fuel cell cost per watt, much attention hasbeen directed to increasing the power output of same. Historically, thishas resulted in additional sophisticated balance-of-plant systems whichare necessary to optimize and maintain high PEM fuel cell power output.A consequence of highly complex balance-of-plant systems is that they donot readily scale down to low capacity applications. Consequently, cost,efficiency, reliability and maintenance expenses are all adverselyeffected in low generation applications.

[0005] It is well known that single PEM fuel cells produce a usefulvoltage of only about 0.45 to about 0.7 volts D.C. per cell under aload. Practical PEM fuel cell plants have been built from multiple cellsstacked together such that they are electrically connected in series. Itis further well known that PEM fuel cells can operate at higher poweroutput levels when supplemental humidification is made available to theproton exchange membrane (electrolyte). In this regard, humidificationlowers the resistance of proton exchange membranes to proton flow. Toachieve this increased humidification, supplemental water can beintroduced into the hydrogen or oxygen streams by various methods, ormore directly to the proton exchange membrane by means of the physicalphenomenon known as of wicking, for example. The focus ofinvestigations, however, in recent years has been to develop membraneelectrode assemblies (MEA) with increasingly improved power output whenrunning without supplemental humidification. Being able to run an MEAwhen it is self-humidified is advantageous because it decreases thecomplexity of the balance-of-plant with its associated costs. However,self-humidification heretofore has resulted in fuel cells running atlower current densities and thus, in turn, has resulted in more of theseassemblies being required in order to generate a given amount of power.

[0006] While PEM fuel cells of various designs have operated withvarying degrees of success, they have also had shortcomings which havedetracted from their usefulness. For example, PEM fuel cell powersystems typically have a number of individual fuel cells which areserially electrically connected (stacked) together so that the powersystem can have a increased output voltage. In this arrangement, if oneof the fuel cells in the stack fails, it no longer contributes voltageand power. One of the more common failures of such PEM fuel cell powersystems is where a membrane electrode assembly (MEA) becomes lesshydrated than other MEAs in the same fuel cell stack. This loss ofmembrane hydration increases the electrical resistance of the effectedfuel cell, and thus results in more waste heat being generated. In turn,this additional heat drys out the membrane electrode assembly. Thissituation creates a negative hydration spiral. The continual overheatingof the fuel cell can eventually cause the polarity of the effected fuelcell to reverse such that it now begins to dissipate electrical powerfrom the rest of the fuel cells in the stack. If this condition is notrectified, excessive heat generated by the failing fuel cell may causethe membrane electrode assembly to perforate and thereby leak hydrogen.When this perforation occurs the fuel cell stack must be completelydisassembled and repaired. Depending upon the design of fuel cell stackbeing employed, this repair or replacement may be a costly, and timeconsuming endeavor.

[0007] Further, designers have long sought after a means by whichcurrent densities in self-humidified PEM fuel cells can be enhancedwhile simultaneously not increasing the balance-of-plant requirementsfor these same devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0009]FIG. 1 is a prospective view of one embodiment of a fuel cellpower system according to the present invention.

[0010]FIG. 2 is an illustrative representation of a control systemcoupled with components of the fuel cell power system.

[0011]FIG. 3 is an exploded perspective view of one configuration of afuel cell cartridge of the fuel cell power system.

[0012]FIG. 4 is a schematic representation of one embodiment ofcircuitry coupled with plural fuel cells of the fuel cell cartridge.

[0013]FIG. 5 is a functional block diagram of one configuration of thecontrol system for the fuel cell power system.

[0014]FIG. 6 is a functional block diagram of a cartridge analysis slavecontroller of the control system coupled with associated circuitry andcomponents.

[0015]FIG. 7 is a functional block diagram of an auxiliary valve slavecontroller of the control system coupled with associated circuitry andcomponents.

[0016]FIG. 8 is a functional block diagram of a fan slave controller ofthe control system coupled with associated circuitry and components.

[0017]FIG. 9 is a functional block diagram of an interface slavecontroller of the control system coupled with associated circuitry andcomponents.

[0018]FIG. 10 is a functional block diagram of an external port slavecontroller of the control system coupled with associated circuitry andcomponents.

[0019]FIG. 11 is a functional block diagram of a system analysis slavecontroller of the control system coupled with associated circuitry andcomponents.

[0020]FIG. 12 is a functional block diagram of a sensor slave controllerof the control system coupled with associated circuitry and components.

[0021]FIG. 13 is a functional block diagram of an air temperature slavecontroller of the control system coupled with associated circuitry andcomponents.

[0022]FIG. 14 is a functional block diagram of a shunt slave controllerof the control system coupled with associated circuitry and components.

[0023]FIG. 15 is a functional block diagram of a switch slave controllerof the control system coupled with associated circuitry and components.

[0024] FIGS. 16-16A are a flow chart illustrating exemplary operationsof a master controller of the control system.

[0025]FIG. 17 is a flow chart illustrating an exemplary start-upoperation of the master controller.

[0026] FIGS. 18-18A are a flow chart illustrating exemplary erroroperations of the master controller.

[0027] FIGS. 19-19B are a flow chart of exemplary operations of thecartridge analysis slave controller.

[0028] FIGS. 20-20A are a flow chart illustrating exemplary operationsof the auxiliary valve slave controller of the control system.

[0029] FIGS. 21-21A are a flow chart illustrating exemplary operationsof the fan slave controller of the control system.

[0030]FIG. 22 is a flow chart illustrating exemplary operations of theinterface slave controller of the control system.

[0031]FIG. 23 is a flow chart illustrating exemplary operations of theexternal port slave controller of the control system.

[0032] FIGS. 24-24A are a flow chart illustrating exemplary operationsof the system analysis slave controller of the control system.

[0033]FIG. 25 is a flow chart illustrating exemplary operations of thesensor slave controller of the control system.

[0034]FIG. 26 is a flow chart illustrating exemplary operations of theair temperature slave controller of the control system.

[0035]FIG. 27 is a flow chart illustrating exemplary operations of theshunt slave controller of the control system.

[0036]FIG. 28 is a flow chart illustrating exemplary operations of theswitch slave controller of the control system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0038] Referring to FIG. 1, one configuration of a fuel cell powersystem 10 is illustrated. The depicted configuration of fuel cell powersystem 10 is exemplary and other configurations are possible. As shown,fuel cell power system 10 includes a housing 12 provided about aplurality of fuel cell cartridges 14. Housing 12 defines a subrackassembly in the described embodiment.

[0039] Fuel cell power system 10 is configured to utilize one or more offuel cell cartridges 14. Twelve such fuel cell cartridges 14 areutilized in the embodiment of fuel cell power 10 described herein. Asdescribed below, individual fuel cell cartridges 14 include a pluralityof fuel cells. In the described configuration, individual fuel cellcartridges 14 include four fuel cells.

[0040] Such fuel cells can comprise polymer electrolyte membrane (PEM)fuel cells. In the described embodiment, the fuel cells can comprisemembrane electrode assembly (MEA) fuel cells or membrane electrodediffusion assembly (MEDA) fuel cells. Further details of oneconfiguration of fuel cells and fuel cell cartridges 14 are described ina co-pending U.S. patent application Ser. No. 08/979,853, entitled “AProton Exchange Membrane Fuel Cell Power System”, filed Nov. 20, 1997,naming William A. Fuglevand, Dr. Shiblihanna I. Bayyuk, Ph. D., Greg A.Lloyd, Peter D. Devries, David R. Lott, John P. Scartozzi, Gregory M.Somers and Ronald G. Stokes as inventors, assigned to the assigneehereof, having attorney docket number WA23-002, and incorporated hereinby reference.

[0041] Housing 12 additionally includes an operator interface 16. In thepresent embodiment, operator interface 16 includes a display 18 andinterface switches 20. Operator interface 16 is configured to indicateoperation of fuel cell power system 10 and also enable an operator tocontrol various functions of fuel cell power system 10.

[0042] Display 18 of operator interface 16 is configured to emit a humanperceptible signal, such as visible signals, to indicate operation offuel cell power system 10. In the depicted embodiment, display 18comprises a plurality of light emitting diode (LED) bar graph arrays toindicate operational conditions of respective fuel cell cartridges 14.In one configuration, individual bar graph arrays of display 18 indicatehigh and low voltages of fuel cells within the corresponding fuel cellcartridge 14.

[0043] Interface switches 20 permit a user to control operations of fuelcell power system 10. For example, one interface switch 20 can beprovided to enable a user to turn on fuel cell power system 10. Inaddition, another interface switch 20 can include a load enable switchwhich permits a user to selectively apply power from fuel cell powersystem 10 to a load 22 coupled with the fuel cell power system 10.Another interface switch 20 can control a cartridge reset functiondescribed below.

[0044] Referring to FIG. 2, some components of fuel cell power system 10are shown. The components are internal and external of housing 12 offuel cell power system 10. Internally, only three fuel cell cartridges14 are shown for purposes of discussion herein. More fuel cellcartridges 14 are provided in typical configurations.

[0045] Fuel cell power system 10 is shown coupled with a remote device24. Fuel cell power system 10 is preferably configured to communicatewith remote device 24. An exemplary remote device 24 comprises anoff-site control and monitoring station. Fuel cell power system 10receives communications from remote device 24 which may comprise dataand commands. Fuel cell power system 10 is also configured to outputdata, requests, etc. to remote device 24.

[0046] The depicted components include the plural fuel cell cartridges14 and operator interface 16 discussed above. In addition, fuel cellpower system 10 includes a control system 30. One configuration ofcontrol system 30 is described below in detail. The illustrated controlsystem 30 is coupled with a power supply sensor 31 associated with apower supply 32, and charge circuitry 34. Control system 30 isadditionally coupled with fuel cell cartridges 14 and operator interface16. Further, control system 30 is coupled with a communication port 36,switching device 38 and current sensor 40. Control system 30 isadditionally coupled with a bleed solenoid 42 associated with a bleedvalve 43.

[0047] The depicted fuel cell power system 10 includes a fuel deliverysystem 28. Fuel delivery system 28 couples with a fuel supply 23 tosupply fuel to fuel cell cartridges 14. Exemplary fuel compriseshydrogen gas in the described embodiment. Other fuels may be possible.

[0048] The depicted fuel delivery system 28 includes a main valve 47 andplural auxiliary valves 45 associated with respective fuel cellcartridges 14. Main valve 47 controls the flow of fuel from fuel supply23 into fuel cell power system 10. Auxiliary valves 45 control the flowof fuel to respective fuel cell cartridges 14. Control system 30 iscoupled with plural auxiliary solenoids 44 of associated auxiliaryvalves 45. Control system 30 is further coupled with a main solenoid 46of associated main valve 47.

[0049] The depicted fuel cell power system 10 includes an airtemperature control assembly 50. The illustrated air temperature controlassembly 50 includes a plenum 51 having associated ports 52corresponding to fuel cell cartridges 14. Within plenum 51 of airtemperature control assembly 50, a temperature modifying element 53, fan54, temperature sensor 55 and fuel sensor 61 are provided.

[0050] A controllable air flow device or air passage 56 couples plenum51 to exterior ambient air outside of housing 12. Air passage 56 canpermit the intake of air into plenum 51 as well as the exhaustion of airfrom plenum 51. Control system 30 is coupled with control circuitry 51of modifying element 53, control circuitry 48 and monitoring circuitry49 of fan 54, temperature circuitry 68 associated with temperaturesensor 55, control circuitry 57 of air passage 56, and heater 75 of fuelsensor 61.

[0051] A first fuel sensor 58 is provided within housing 12 and outsideof plenum 51 as shown. First fuel sensor 58 is operable to monitor forthe presence of fuel within housing 12. A second fuel sensor 61 isprovided within plenum 51 to monitor for the presence of fuel withinplenum 51. Control system 30 is configured to couple with fuel detectioncircuitry 64 associated with fuel sensors 58, 61. Fuel detectioncircuitry 64 can condition measurements obtained from sensors 58, 61.

[0052] Heaters 74, 75 are coupled with respective fuel sensors 58, 61 toprovide selective heating of fuel sensors 58, 61 responsive to controlfrom control system 30. Heaters 74, 75 are integral of fuel sensors 58,61 in some configurations. An exemplary fuel sensor configuration withan integral heater has designation TGS 813 available from FigaroEngineering, Inc. Such heaters are preferably provided in a predefinedtemperature range to assure proper operation. Other configurations ofsensors 58, 61 are possible.

[0053] An external temperature sensor 59 is provided outside of housing12 in one embodiment. Control system 30 is also coupled with temperaturecircuitry 67 associated with temperature sensor 59 to monitor theexterior temperature. Temperature circuitry 67 conditions signalsreceived from temperature sensor 59.

[0054] Control system 30 is configured to at least one of control andmonitor at least one operation of fuel cell power system 10. Duringoperation, fuel from fuel supply 23 is applied to main valve 47. Mainvalve 47 is coupled with auxiliary valves 45 as shown. Responsive tocontrol from control system 30, main valve 47 and auxiliary valves 45apply fuel to respective fuel cell cartridges 14. Responsive to thesupply of fuel, and in the presence of oxygen, fuel cell cartridges 14produce electrical power.

[0055] A power bus 60 couples the fuel cell cartridges 14 in series.Power bus 60 is coupled with external terminals 62, 63 which may beconnected with an external load 22 (shown in FIG. 1). Terminal 62provides a positive terminal and terminal 63 provides a negativeterminal of fuel cell power system 10.

[0056] Air temperature control assembly 50 applies oxygen to therespective fuel cell cartridges 14 via ports 52. Fuel cell cartridges 14are individually operable to convert chemical energy into electricity.As described below, fuel cartridges 14 individually contain plural fuelcells individually having an anode side and a cathode side. Auxiliaryvalves 45 apply fuel to the anode sides of the fuel cells. Plenum 51directs air within the cathode sides of the fuel cells.

[0057] Air temperature control assembly 50 preferably providescirculated air within a predetermined temperature range. Such circulatedair can be exterior air and/or recirculated air. In the preferredembodiment, air temperature control assembly 50 provides air withinplenum 51 within an approximate temperature range of 25° Celsius to 80°Celsius.

[0058] Upon start-up conditions of fuel cell power system 10, modifyingelement 53 may be controlled via control system 30 using element controlcircuitry 41 to either increase or decrease the temperature of airpresent within plenum 51. Fan 54 operates to circulate the air is withinplenum 51 to respective fuel cell cartridges 14. Fan control circuitry48 and fan monitor circuitry 49 are shown coupled with fan 54.Responsive to control from control system 30, fan control circuitry 48operates to control air flow rates (e.g., speed of rotation) of fan 54.Fan monitor circuitry 49 operates to monitor the actual air flow ratesinduced by fan 54 (e.g., circuitry 49 can comprise a tachometer forrotational fan configurations).

[0059] Control system 30 monitors the temperature of the air withinplenum 51 using temperature sensor 55. During operation, heat isgenerated and emitted from fuel cell cartridges 14. Thus, it may benecessary to decrease the temperature of air within plenum 51 to provideefficient operation of fuel cell power system 10. Responsive to controlfrom control system 30, air passage 56 can be utilized to introduceexterior air into plenum 51 and exhaust air from plenum 51 to ambient.

[0060] Control system 30 communicates with control circuitry 57 tocontrol air passage 56. In one embodiment, air passage 56 includes aplurality of vanes and control circuitry 57 operates to control theposition of the vanes of air passage 56 to selectively introduceexterior air into plenum 51. The vanes of air passage 56 can preferablybe provided in a plurality of orientations between an open position anda closed position to vary the amount of exterior fresh air introducedinto plenum 51 or the amount of air exhausted from plenum 51 responsiveto control from control system 30. Air circulated within plenum 51 cancomprise recirculated and/or fresh ambient air.

[0061] Utilizing temperature sensor 59, control system 30 can alsomonitor the temperature of ambient air about housing 12. Control system30 can utilize such exterior temperature information from temperaturesensor 59 to control the operation of air passage 56. Temperature sensor59 is located adjacent air passage 56 in a preferred embodiment.

[0062] As described in further detail below, control system 30 controlsair flow rates of fan 54 using fan control circuitry 48. Fan monitorcircuitry 49 provides air flow rate information to control system 30.Control system 30 can monitor the total system voltage being deliveredvia power bus 60 by summing the individual cell voltages. Control system30 can also monitor the electrical load being delivered via power bus 60using current sensor 40. With knowledge of the system bus voltage andload, control system 30 can calculate waste thermal power and provide adesired cooling air flow.

[0063] More specifically, the efficiency of one or more fuel cells maybe determined by dividing the respective fuel cell voltage by 1.23 (atheoretical maximum voltage of a single fuel cell). An averageefficiency can be determined for all fuel cells 90 of fuel cell powersystem 10. The remaining energy (energy not associated to electricity)as determined from the efficiency calculation is waste thermal power.The determined waste thermal power may be utilized to provide a desiredcooling air flow. Control system 30 controls the air flow rates of fan54 depending upon the waste thermal power in accordance with one aspectof the described fuel cell power system 10.

[0064] During operation of fuel cell cartridges 14, non-fuel diluentssuch as cathode-side water and atmospheric constituents can diffuse fromthe cathode side of the fuel cell through a membrane electrode assemblyof the fuel cell and accumulate in the anode side of the fuel cell. Inaddition, impurities in the fuel supply delivered directly to the anodeside of the fuel cell also accumulate. Without intervention, thesediluents can dilute the fuel sufficiently enough to degrade performance.Accordingly, the anode side of the individual fuel cells is connected toa bleed manifold 65. Bleed manifold 65 is additionally coupled withbleed valve 43.

[0065] Control system 30 selectively operates bleed solenoid 42 toselectively open and close bleed valve 43 permitting exhaustion ofmatter such as entrained diluents and perhaps some fuel via a bleedexhaust 66 within housing 12. Control system 30 can operate to open andclose bleed valve 43 on a periodic basis. The frequency of openings andclosings of bleed valve 43 can be determined by a number of factors,such as electrical load coupled with terminals 62, 63, etc. Although notshown, a fuel recovery system may be coupled with bleed exhaust 66 toretrieve unused fuel for recirculation or other uses.

[0066] Following a start-up condition either inputted via interface orfrom remote device 24, control system 30 selectively controls switchingdevice 38 to couple power bus 60 with positive terminal 62. Switchingdevice 38 can comprise parallel MOSFET switches to selectively couplepower bus 60 with an external load 22.

[0067] For example, control system 30 may verify when an appropriateoperational temperature within plenum 51 has been reached utilizingtemperature sensor 55. In addition, control system 30 can verify that atleast one electrical characteristic, such as voltage and/or current, ofrespective fuel cell cartridges 14 has been reached before closingswitching device 38 to couple power bus 60 with an associated load 22.Such provides proper operation of fuel cell power system 10 beforecoupling bus 60 with an external load 22.

[0068] Power supply 32 includes power supplies having different voltagepotentials in the described embodiment. For example, power supply 32 canprovide a 5-volt supply voltage for operating the digital circuitry offuel cell power system 10, such as control system 30. Power supply 32can also provide higher voltage potentials, such as ±12 volts foroperation of components such as fan 54 within fuel cell power system 10.

[0069] Further, power supply 32 can include a battery poweringcomponents during start-up procedures. Following start-up procedures,power supply 32 can be coupled with power bus 60 and internal powerutilized by fuel cell power system 10 can be derived from electricalpower generated from fuel cell cartridges 14. Charge circuitry 34 isprovided to selectively charge batteries of power supply 32 utilizingpower from power bus 60. Control system 30 is configured to monitorelectrical conditions of the batteries and the supplied voltages ofpower supply 32 using power supply sensors 31. Control system 30 canoperate charge circuitry 34 to charge batteries of power supply 32depending upon such monitoring operations.

[0070] Control system 30 is also coupled with communication port 36providing communications to an external device such as a remote device24. An exemplary remote device 24 comprises an external control systemor monitoring system off-site from fuel cell power system 10. Controlsystem 30 can output data including requests, commands, operationalconditions, etc., of fuel cell power system 10 using communication port36. In addition, control system 30 can receive data including commands,requests, etc., from remote device 24 using communication port 36.

[0071] Referring to FIG. 3, an exemplary fuel cell cartridge 14 isshown. Further details of fuel cell cartridge 14 are disclosed in detailin U.S. patent application Ser. No. 08/979,853 incorporated by referenceabove. The depicted fuel cell cartridge 14 includes a fuel distributionframe 70 and a force application assembly which includes plural cathodecovers 71 which partially occlude respective cavities housing membraneelectrode assemblies (MEA) or membrane electrode diffusion assemblies(MEDA) within fuel distribution frame 70. The depicted fuel cellcartridge 14 includes four fuel cells (individually shown as referencenumeral 90 in FIG. 4). Other configurations are possible.

[0072] The respective cathode covers 71 individually cooperate orotherwise mate with each other, and with the fuel distribution frame 70.Individual apertures 72 which are defined by the cathode cover, definepassageways 73 which permit air from plenum 51 to circulate to thecathode side of the membrane electrode diffusion assembly containedwithin fuel distribution frame 70. The circulation of air through thefuel cell cartridge 14 is discussed in significant detail in U.S. patentapplication Ser. No. 08/979,853 incorporated by reference above.

[0073] Conductive members 63 extend outwardly from a main body ofindividual fuel cells within fuel cell cartridge 14. Conductive members63 are designed to extend through respective gaps or openings which areprovided in fuel distribution frame 70. Each conductive member 63 isreceived between and thereafter electrically coupled with pairs ofconductive contacts which are mounted on a rear wall of a subrackdescribed in greater detail below.

[0074] Fuel cell cartridge 14 is operable to be serially electricallycoupled with a plurality of other fuel cell cartridges 14 by way of asubrack which is generally indicated by the numeral 76. Subrack 76 has amain body 77 having top and bottom portions 78, 79, respectively. Thetop and bottom portions are joined together by a rear wall 80. Elongatedchannels 81 are individually formed in top and bottom portions 78, 79and are operable to slidably receive individual spines 74 which areformed on fuel distribution frame 70.

[0075] Subrack 76 is made of a number of mirror image portions 85, whichwhen joined together, form the main body 77 of subrack 76. These mirrorimage portions 85 are fabricated from a moldable dielectric substrate.Power bus 60 is affixed on rear wall 80 of the subrack 90. A repeatingpattern of eight pairs of conductive contacts 84 are attached on rearwall 80 and are coupled with power bus 60. Electrical coupling of fuelcells within fuel cell cartridge 14 with power bus 60 is implementedusing contacts 84 in the described embodiment.

[0076] First and second conduits 86, 87 are also attached to rear wall80 and are operable to matingly couple in fluid flowing relation to thefuel distribution frame 70. The respective first and second conduits 86,87 extend through rear wall 80 and connect with suitable externalconduits (not shown). First conduit 86 is coupled in fluid flowingrelation with fuel supply 23 (FIG. 1) and with anode sides of internalfuel cells. Further, second conduit 87 exhausts from the anode sides ofthe fuel cells to bleed manifold 65 (FIG. 2).

[0077] Individual fuel cell cartridges 14 may be selectivelydeactivated. For example, fuel cell cartridges 14 are individuallyphysically removable from fuel cell power system 10. Removal of one ormore fuel cell cartridges 14 may be desired for maintenance,replacement, etc. of the fuel cell cartridges 14. The remaining fuelcell cartridges 14 and internal fuel cells thereof may continue tosupply power to an associated load 22 with one or more of the fuel cellcartridges 14 deactivated.

[0078] Individual contacts 84 may be configured to maintain electricalcontinuity of bus 60 upon physical removal of a fuel cell cartridge 14from an associated subrack 76. As shown, individual contacts 84 comprisemake before break contacts which individually include plural conductivemembers configured to receive an associated contact 69 of a fuel cellcartridge 14. Individual contacts 69 can comprise a tang or knife. Uponphysical removal of fuel cell cartridge 14 and the correspondingterminals 69, conductive members of contacts 84 are mechanically coupledtogether to maintain a closed circuit within bus 60 intermediateterminals 62, 63. Such maintains a supply of electrical power to load 22coupled with terminals 62, 63 during removal of one or more fuel cellcartridges 14 from fuel cell power system 10.

[0079] Referring to FIG. 4, a schematic representation of four fuelcells 90 of a fuel cell cartridge 14 is shown. Individual fuel cells 90have plural contacts 84 as described above. Fuel cells 90 are typicallycoupled in series using power bus 60. Control system 30 is configured tomonitor at least one electrical characteristic of individual fuel cells90 using analysis circuitry 91 in the described embodiment.

[0080] More specifically, analysis circuitry 91 includes a voltagesensor 92 which may be provided electrically coupled with contacts 84 asshown. Such coupling enables voltage sensor 92 to monitor the voltagesof the individual respective fuel cells 90. Fuel cells 90 have beenobserved to typically produce a useful voltage of about 0.45 to about0.7 volts DC under a typical load.

[0081] An exemplary configuration of voltage sensor 92 is implemented asa differential amplifier for monitoring voltages. Voltage sensor 92 ispreferably configured to monitor voltage magnitude across individualfuel cells 90 as well as polarity of individual fuel cells 90.

[0082] Analysis circuitry 91 can additionally include plural currentsensors 94, 97. Individual current sensors may be coupled with contacts84 of individual fuel cells 90 to monitor current flowing throughrespective individual fuel cells 90 in an alternative arrangement (notshown). Control system 30 is coupled with current sensors 94, 97 and isconfigured to monitor corresponding respective currents through fuelcells 90 and outputted to load 22 via bus 60.

[0083] Current sensor 94 is coupled intermediate one of fuel cells 90and a coupling with internal power supply 93. Current sensor 94 iscoupled intermediate the coupling with internal power supply 93 andexternal terminal 62 coupled with an associated load.

[0084] Following start-up operations, power for internal use within fuelcell power system 10 (e.g., power provided to the circuitry of controlsystem 30) is provided from fuel cell cartridges 14. Internal powersupply 93 extracts current from bus 60 as shown to provide internalpower to fuel cell power system 10.

[0085] Accordingly, current sensor 94 provides information regardingcurrent flow through serially coupled fuel cell cartridges 14. Currentsensor 97 provides information regarding current flow to a load coupledwith terminal 62 (i.e., load 22 shown in FIG. 1).

[0086] Plural switching devices 96 are also provided which correspond torespective fuel cells 90. Switching devices 96 can be individuallyprovided intermediate contacts 84 of respective fuel cells 90 asillustrated. In the depicted configuration, switching devices 96 cancomprise MOSFET devices. Gate electrodes of switching devices 96 arecoupled with control system 30.

[0087] Control system 30 is operable to selectively shunt electrodes 84using switching devices 96 corresponding to a desired one or more offuel cells 90 to electrically bypass or deactivate such fuel cells 90.For example, if control system 30 observes that an electricalcharacteristic (e.g., voltage) of a fuel cell 90 as sensed via sensors92, 94 is below a desired range, control system 30 can instruct arespective switching device 96 to turn on and shunt the respective fuelcell 90. In addition, individual fuel cells 90 can be selectivelyshunted using respective switching devices 96 to enhance the performanceof fuel cells 90.

[0088] In one configuration, fuel cells 90 can be shunted according to aduty cycle. The duty cycle may be adjusted by control system 30depending upon operation of fuel cell cartridges 14 and fuel cell powersystem 10. Fuel cells 90 can be shunted by sequential order asdetermined by control system 30. Shunting is also helpful during startupoperations to generate heat within housing 12 to bring fuel power system10 up to operating temperature in an expedient manner.

[0089] Alternatively, individual fuel cells 90 may be shunted forextended periods of time if control system 30 observes such fuel cellsare operating below desired ranges (e.g., low voltage conditions,reverse polarity conditions). Shunting operations are discussed inco-pending U.S. patent application Ser. No. 09/108,667, entitledImproved Fuel Cell and Method for Controlling Same”, filed on Jul. 1,1998, naming William A. Fuglevand, Peter D. Devries, Greg A. Lloyd,David R. Lott, and John P. Scartozzi as inventors, assigned to theassignee hereof, having attorney docket number WA23-005, andincorporated herein by reference.

[0090] Referring to FIG. 5, one configuration of control system 30 isillustrated. In the depicted arrangement, control system 30 includes adistributed control system including a plurality of controllers 100-120.Individual controllers 100-120 comprise programmable microcontrollers inthe described embodiment. Exemplary microcontrollers have tradedesignation MC68HC705P6A available from Motorola, Inc. In the describedembodiment, controllers 100-120 individually comprise a controllerconfigured to execute instructions provided within executable code. Inan alternative configuration, the steps described with reference toFIGS. 16-28 below are implemented within hardware.

[0091] Individual controllers can include random access memory (RAM),read only memory (ROM), analog-to-digital (A/D) converters, serialinput/output port (SIOP) communications, timers, digital input/ output(I/O), timer interrupts and external interrupts. Individual controllers102-120 have internal digital processing circuitry configured to executea set of software or firmware instructions. Such instructions can bestored within the internal read only memory of the respectivecontrollers 100-120. Other configurations of control system 30 arepossible.

[0092] Among other functions, master controller 100 functions as acommunication router to implement communications intermediate mastercontroller 100 and individual slave controllers 102-120. In thedescribed embodiment, communications are implemented in a limitedfull-duplex mode. Other communication protocols may be utilized.

[0093] Master controller 100 outputs messages to slave controllers102-120. Outputted messages are seen by all slave controllers 102-120.Individual slaves 102-120 identified by the outgoing message process thecorresponding message. Thereafter, receiving slave controllers 102-120can output a message to master controller 100. In addition, mastercontroller 100 can sequentially poll slave controllers 102-120 todetermine whether such slave controllers 102-120 have communications formaster controller 100. Master controller 100 can also supply clockinformation to slave controllers 102-120 to establish a common timingreference within control system 30.

[0094] Individual slave controllers 102-120 perform specific tasks incontrol system 30 including a plurality of distributed controllers.Individual slave controllers 102-120 can monitor specified functions offuel cell power system 10 and report to master controller 100. Further,master controller 100 can direct operations of individual slavecontrollers 102-120.

[0095] Referring to FIG. 6, cartridge analysis slave controller 102 iscoupled with master controller 100 and associated circuitry. Inparticular, cartridge analysis slave controller 102 is coupled withanalysis circuitry 91 which is in turn coupled with fuel cells 90 andpower bus 60 as previously described. Utilizing voltage sensor 92 andcurrent sensor 94 of analysis circuitry 91, cartridge analysis slavecontroller 102 can monitor electrical characteristics such as thevoltage of individual fuel cells 90 as well as the current through fuelcells 90. Further, cartridge analysis slave controller 102 can monitorcurrent flowing through power bus 60 to load 22 using current sensor 97of analysis circuitry 91. As described below, cartridge analysis slavecontroller 102 can communicate such electrical characteristics to mastercontroller 100.

[0096] Referring to FIG. 7, auxiliary valve slave controller 104 isshown coupled with master controller 100 and auxiliary solenoids 44 andbleed solenoid 42. In turn, auxiliary solenoids 44 are coupled withauxiliary valves 45 and bleed solenoid 42 is coupled with bleed valve 43as discussed above. Responsive to control communications from mastercontroller 100, auxiliary valve slave controller 104 is configured tooperate auxiliary solenoids 44 and bleed solenoid 42 to controlauxiliary valves 45 and bleed valve 43, respectively.

[0097] Referring to FIG. 8, fan slave controller 106 is coupled with fancontrol circuitry 48 and fan monitor circuitry 49. As described above,fan control circuitry 48 and fan monitor circuitry 49 are individuallycoupled with fan 54. Upon receiving instruction from master controller100, fan slave controller 106 is operable to control operation of fan 54using fan control circuitry 48. For example, fan slave controller 106controls on/off operational modes of fan 54 and the air flow rate of fan54. Using fan monitor circuitry 49, fan slave controller 106 can monitoroperation of fan 54. Fan slave controller 106 can output fan statusinformation (e.g., RPM for a rotational fan) to master controller 100.

[0098] Referring to FIG. 9, interface slave controller 108 is coupledwith master controller 100 and operator interface 16. Master controller100 supplies operational status information from other slave controllersto interface slave controller 108. Thereafter, interface slavecontroller 108 can control operator interface 16 to convey such statusinformation to an operator. Exemplary indications can include a lightemitting diode (LED) array, bar graph display, audio warning buzzer,etc.

[0099] Referring to FIG. 10, external port slave controller 110 iscoupled with communication port 36 and memory 37 as well as mastercontroller 100. As described previously, communication port 36 isadditionally coupled with a remote device 24. Communication port 36 andmemory 37 operate to provide bidirectional communications intermediateexternal port slave controller 110 and remote device 24. Although memory37 is shown external of external port slave controller 110, in someconfigurations such memory 37 can be implemented as internal circuitryof external port slave controller 110.

[0100] Memory 37 operates to buffer data passing to remote device 24 ordata received from remote device 24 within external port slavecontroller 110. External port slave controller 110 operates to forwardreceived communications to master controller 100 according to timing ofmaster controller 100. External port slave controller 110 operates tooutput messages from master controller 100 to remote device 24 usingcommunication port 36 according to an agreed-upon communication protocolintermediate external port slave controller 110 and remote device 24.

[0101] Referring to FIG. 11, system slave controller 112 is coupled withmaster controller 100 as well as main solenoid 46, charge circuitry 34,power supply sensors 31, current sensor 40 and element control circuitry41. Responsive to control from master controller 100, system slavecontroller 112 is configured to control the operation of main valve 47using main solenoid 46. Further, responsive to control from mastercontroller 100, system slave controller 112 can selectively charge abattery 35 of power supply 30 using charge circuitry 34.

[0102] Slave controller 112 can implement the charging of battery 35responsive to information from power supply sensors 31. Power supplysensors 31 provide electrical characteristic information of battery 35and internal power sources 39 to system slave controller 112. Internalpower sources 39 of power supply 32 include the 5 Volt DC source and ±12Volt DC source previously described.

[0103] Using current sensor 40, system slave controller 112 can monitorcurrent flowing through power bus 60. Such provides load information andoutput power of fuel cell power system 10 to system slave controller112. Thereafter, system slave controller 112 can provide such currentand load information to master controller 100.

[0104] System slave controller 112 is also coupled with element controlcircuitry 41 utilized to control modifying element 53. Such is utilizedto control the temperature within plenum 51. Modifying element 53 can becontrolled to provide circulated air within plenum 51 within a desiredoperational temperature range. Modifying element 53 is advantageouslyutilized in some start-up situations to bring the temperature withinplenum 51 within the operational range in an expedient manner.

[0105] Referring to FIG. 12, sensor slave controller 114 is coupled withmaster controller 100, heaters 74, 75, fuel detection circuitry 64 andtemperature circuitry 67. Fuel detection circuitry 64 is associated withplural fuel sensors 58, 61 provided within housing 12 and plenum 51,respectively. Temperature circuitry 67 is coupled with temperaturesensor 59 located outside of housing 12. Sensor slave 114 can controlheaters 74, 75 to selectively bring fuel sensors 58, 61 within anappropriate temperature range for operation.

[0106] Fuel detection circuitry 64 receives data from fuel sensors 58,61 and can condition such information for application to sensor slavecontroller 114. If fuel is detected using fuel sensors 58, 61, fueldetection circuitry 64 can process such information and provide suchdata to sensor slave controller 114. Such information can indicate theconcentration of fuel detected within housing 12 or plenum 51 using fuelsensors 58, 61, respectively. Sensor slave controller 114 can in turnprovide such information to master controller 100.

[0107] Temperature sensor 59 provides information regarding thetemperature of the surroundings of fuel cell power system 10.Temperature circuitry 67 receives outputted signals from temperaturesensor 59 and can condition such signals for application to sensor slavecontroller 114 monitoring the external temperature. Sensor slavecontroller 114 can provide external temperature information to mastercontroller 100.

[0108] Referring to FIG. 13, air temperature slave controller 116 iscoupled with master controller 100 and temperature circuitry 68 andpassage control circuitry 57. Temperature circuitry 68 is associatedwith temperature sensor 55 provided within plenum 51. Passage controlcircuitry 57 operates to control air passage 56. For example, passagecontrol circuitry 57 can control the position of vanes of air passage 56in an exemplary embodiment.

[0109] Temperature sensor 55 is positioned within plenum 51 to monitorthe temperature of circulated air within plenum 51. Temperaturecircuitry 68 receives the sensor information from temperature sensor 55and conditions the information for application to air temperature slavecontroller 116. Thereafter, air temperature slave controller 116 mayoperate to output the temperature information to master controller 100.

[0110] During operation of fuel cell power system 10, air temperatureslave controller 116 operates to control the flow of air into housing 12using air passage 56 as well as the exhaustion of air within plenum 51to the exterior of housing 12. Air temperature slave controller 116controls air passage 56 using passage control circuitry 57 to maintainthe temperature of circulated air within plenum 51 within the desiredoperational temperature range. Further, modifying element 63 of FIG. 11can be controlled as previously discussed to raise or lower thetemperature of the circulated air. Such control of air passage 56 by airtemperature slave controller 116 can be responsive to information fromtemperature sensor 55 and external temperature sensor 59. Further,efficiency information regarding fuel cells 90 can be calculated by airtemperature slave controller 116 to determine waste thermal power. Airpassage 56 may be controlled responsive to the calculated waste thermalpower.

[0111] Referring to FIG. 14, shunt slave controller 118 is coupled withmaster controller 100 and switch control circuitry 95. Plural switchingdevices 96 are coupled with switch control circuitry 95. As describedabove, switching devices 96 are provided to implement selective shuntingof respective fuel cells 90 of fuel cell cartridges 14. Mastercontroller 100 can be configured to output shunt information to shuntslave controller 118 for selectively shunting using switching devices96. Alternatively, shunt slave controller 118 can execute internallystored code to provide controlled selective shunting of switchingdevices 96:

[0112] Such shunting operations of fuel cells 90 can be utilized toprovide increased power, to expedite start-up procedures, to shunt afaulty fuel cell cartridge 14, and to monitor for fuel leaks inexemplary embodiments. Switch control circuitry 95 is provided toprovide conditioning of control signals intermediate shunt slavecontroller 118 and switching devices 96.

[0113] Referring to FIG. 15, switch stave controller 120 is coupled withmaster controller 100 and switch control circuitry 33 and switchconditioning circuitry 19. Switch control circuitry 33 is coupled withswitching device 38 provided in series with power bus 60. Responsive tomaster controller 100, switch slave controller 120 can instruct switchcontroller circuitry 33 to control switching device 38. Switching device38 provides selective coupling of power bus 60 to an external load 22.Such can be utilized to assure proper operation of fuel cell powersystem 10 prior to coupling power bus 60 with load 22.

[0114] Switch slave controller 120 can also monitor the status ofoperator interface switches 20 which may be set by an operator of fuelcell power system 10. Exemplary switches include power on/off of fuelcell power system 10, enable load, cartridge reset, etc. Switchconditioning circuitry 19 can filter signals provided from switches 20and provide corresponding information regarding switch position toswitch slave controller 120. Thereafter, switch slave controller 120 canoutput the switch status information to master controller 100.

[0115] Referring to FIGS. 16-16A, a flow chart illustrating exemplaryoperations of master controller 100 of control system 30 is shown.Initially, master controller 100 performs a communications check at stepS10. Communication checks may be implemented on a periodic interruptbasis to verify communications of master controller 100 and slavecontrollers 102-120.

[0116] At step S12, master controller 100 determines whether acommunication error was discovered. If such an error is present, mastercontroller 100 issues a shut down command to slave controllers 102-120at step S14. Respective slave controllers 102-120 implement shut downoperations to bring fuel cell power system 10 into a shut downcondition. Interface slave controller 108 can indicate the shut downstatus using operator interface 16. Further, master controller 100 caninstruct external port slave controller 110 to notify remote device 24of the shut down condition.

[0117] Alternatively, if no communication error is present in step S12,master controller 100 instructs system slave controller 112 to open mainvalve 47 at step S16. In addition, master controller 100 instructs fanslave controller 106 to start fan 54 at step S16. At step S18, mastercontroller 100 instructs auxiliary valve slave controller 104 to openauxiliary valves 45 using auxiliary solenoids 44. Next, mastercontroller 100 issues a command to auxiliary valve slave controller 104to open bleed valve 43 using bleed solenoid 42 at step S20.

[0118] Thereafter, master controller 100 may execute a start-upsubroutine as set forth in FIG. 17 at step S22. Following successfulexecution of the start-up subroutine, master controller 100 outputs aload enable “ready” signal to switch slave controller 120 at step S24.Switch slave controller 120 controls, using switch control circuitry 33,switching device 38 to couple power bus 60 with an external load.

[0119] At step S26 of FIG. 16A, master controller 100 extracts data fromslave controllers 102-120. More specifically, master controller 100 canreceive information from cartridge analysis slave controller 102,auxiliary valve slave controller 104, fan slave controller 106, externalport slave controller 110, system slave controller 112, sensor slavecontroller 114, air temperature slave controller 116 and switch slavecontroller 120.

[0120] Next, master controller 100 proceeds to step S28 where it isdetermined if a cartridge reset request has been issued. An operator canimplement a cartridge reset condition using switches 20. If a cartridgereset is indicated, master controller 100 proceeds to step S30 andissues an on-line command to change the status of all off-line fuel cellcartridges 14 to being on-line. Thereafter, master controller 100initiates a bleed cycle utilizing auxiliary valve slave controller 104at step S32. During the bleed cycle, fuel may be applied to individualfuel cell cartridges 14 and the bleed valve 43 can be opened to allowexhaust operations using bleed manifold 65 and bleed exhaust 66.

[0121] If no cartridge reset request is indicated at step S28, or afterthe bleed cycle is initiated at step S32, master controller 100 proceedsto step S34 to determine whether a communication error is present. If acommunication error is present, master controller 100 issues a shut downcommand at step S36.

[0122] If no communication error is present at step S34, mastercontroller 100 proceeds to step S38 to execute an error subroutine asdescribed in FIGS. 18-18A below. At step S40, master controller 100calculates operating parameters utilizing the data obtained at step S26.Based upon the calculated operating parameters (e.g., setting of fan 54,modifying element 53, etc.), master controller 100 sends the systemsettings at step S42 to the appropriate slave controllers 102-120.

[0123] Referring to FIG. 17, a start-up subroutine executable by mastercontroller 100 is described. Initially, data from sensor slavecontroller 114 is analyzed to determine whether the temperature withinplenum 51 is less than 15° Celsius. If yes, master controller 100 turnson modifying element 53 utilizing system slave controller 112 at stepS52. Alternatively, master controller 100 instructs systems slavecontroller 112 to turn off modifying element 53 if appropriate at stepS54.

[0124] Thereafter, master controller 100 proceeds to step S56 andinstructs shunt slave controller 118 to set a shunting duty cycle tomaximum. At step S58, master controller 100 again retrieves thetemperature within plenum 51 from air temperature slave controller 116.At step S58, master controller 100 determines whether the temperaturewithin plenum 51 is less than 30° Celsius. If so, master controllerloops at step S58 until the temperature within plenum 51 is equal to orgreater 30° Celsius. Next, at step S60, master controller 100 cancalculate a new duty cycle for application to shunt slave controllers118. Thereafter, master controller 100 returns to the main set ofinstructions described in FIGS. 16-16A.

[0125] Referring to FIGS. 18-18A, a flow chart illustrating exemplaryerror operations of master controller 100 is illustrated. Initially, atstep S62, master controller 100 determines whether fan operation isproper. Master controller 100 observes data from fan slave controller106 and outputs a fan error message to interface slave controller 108 atstep S64 if fan operation is not proper. Thereafter, a shut down commandis issued at step S66 to initiate a shut down procedure of fuel cellpower system 10.

[0126] At step S68, it is determined whether internal power supplies areoperating properly. More specifically, master controller 100 interfaceswith system slave controller 112 to determine whether values monitoredby power supply sensors 31 are within range. If not, master controller100 sends a power supply error message to interface slave controller 108at step S70. Thereafter, master controller 100 issues a shut downcommand at step S72.

[0127] At step S74, master controller 100 determines whether auxiliaryvalve operation is proper. Such is determined by data received fromauxiliary valve slave controller 104 regarding the status of auxiliaryvalves 45. This can be additionally performed by monitoring the voltageof a deactivated fuel cell 90. A zero voltage should result if auxiliaryvalve operation is proper. Master controller 100 outputs an auxiliaryvalve error message at step S76 to interface slave controller 108 ifoperation is not proper. Such error message can thereafter be displayedusing operator interface 16. At step S78, master controller 100 issues ashut down command.

[0128] Alternatively, master controller 100 proceeds to step S80 anddetermines whether a major fuel leak is present. Such is determined bymonitoring data received from sensor slave controller 114 responsive tothe monitoring of fuel sensors 58, 61. If a major fuel leak is detected,master controller 100 sends a major fuel leak error message to interfaceslave controller 108 at step S82. Thereafter, a shut down command isissued at step S84.

[0129] If no major fuel leak is determined, master controller 100proceeds to step S86 to determine whether a minor fuel leak is present.In one configuration, a major fuel leak may be defined as ≧5000 ppm anda minor fuel leak may be defined as 1000-4999 ppm. In some applications,the ranges may be varied for increased or decreased sensitivity to fuel.

[0130] If a minor fuel leak is determined at step S86, master controller100 proceeds to step S88 to try to determine if one of fuel cellcartridges 14 is faulty and the source of the fuel leak. Accordingly, afirst fuel cell cartridge 14 is deactivated at step S88. Next, mastercontroller 100 attempts to determine whether the fuel leak is gone.Deactivation of the fuel cell cartridge 14 ceases the supply of fuel tothe fuel cell cartridge 14 using the appropriate auxiliary valve 45. Ifit is determined that the fuel leak is gone, an error message is sent atstep S92 to interface slave controller 108 for conveyance to operatorinterface 16.

[0131] If the fuel leak remains as determined at step S90, mastercontroller 100 proceeds to step S94 to reactivate the previouslydeactivated fuel cell cartridge 14 and deactivate a subsequent fuel cellcartridge 14. At step S96, master controller 100 determines whether anindex has led past the last fuel cell cartridge 14. If not, mastercontroller 100 returns to steps S90-S94 to continue with the minor leakanalysis. Alternatively, master controller 100 proceeds to step S98 andignores the minor leak for a specified period of time. Once thespecified period of time has elapsed, and the fuel leak is stillpresent, master controller 100 can issue a shut down command which willcease the supply of fuel from fuel supply 23 into housing 12 using mainvalve 47.

[0132] At step S100, master controller 100 determines whether there is afailed fuel cell cartridge 14. If so, master controller 100 shuts offthe supply fuel to the failed fuel cell cartridge 14 using theappropriate auxiliary valve 45 at step S102. In addition, a full-timeshunt command for the failed fuel cell cartridge 14 is applied to shuntslave controller 118 at step S104. At step S106, master controller 100sends an error message to interface slave controller 108 for conveyanceusing operator interface 16.

[0133] At step S108, master controller 100 determines whether enoughfuel cell cartridges 14 are currently on-line. In one exemplaryarrangement, master controller 100 determines whether less than eightfuel cell cartridges 14 are on-line. If not enough cartridges areon-line, master controller 100 sends an error command at step S110 tointerface slave controller 108. Such error message can be conveyed to anoperator using operator interface 16. Next, at step S112, mastercontroller 100 issues a shut down command for fuel cell power system 10.If enough fuel cell cartridges 14 are on-line at step S108, mastercontroller 100 proceeds to the main set of instructions defined in theflow chart of FIGS. 16-16A.

[0134] Referring to FIGS. 19-19B, a flow chart illustrating exemplaryoperations of cartridge analysis slave controller 102 is shown.Initially, at step S120, slave controller 102 indexes to a first fuelcell 90 within fuel cell power system 10. A transient counter describedbelow is cleared at step S121. Slave controller 102 obtains a voltagereading of the indexed fuel cell 90 at step S122. At step S124, slavecontroller 102 determines whether the polarity of the indexed fuel cell90 is proper. If not, slave controller 102 proceeds to step S126 andsets the indicated fuel cell voltage to zero. Thereafter, the voltagefor the currently indexed fuel cell 90 is posted to a fuel cell array atstep S134.

[0135] Alternatively, if the polarity of the indexed fuel cell 90 isproper at step S124, slave controller 102 determines whether the voltageis proper at step S128. If not, slave controller 102 increments aridethrough transient counter at step S130. Thereafter, slave controller102 determines whether the transient counter is at a maximum value atstep S132. If not, slave controller 102 returns to step S122. If thetransient counter has reached a maximum value, slave controller 102proceeds to step S134 to post the voltage to the fuel cell array.

[0136] At step S136, slave controller 102 determines whether all of thefuel cells 90 have been indexed. If not, slave controller 102 indexes toa next fuel cell 90 at step S138 and thereafter returns to step S122. Ifall fuel cells 90 have been analyzed using analysis circuitry 91, slavecontroller 102 proceeds to step S140 to arrange the fuel cell readingsinto readings for respective fuel cell cartridges 14.

[0137] Next, slave controller 102 proceeds to step S141 to index to afirst of fuel cell cartridges 14. Slave controller 102 then proceeds tostep S142 to determine whether any of the fuel cell cartridges 14 werepreviously provided in a down or off-line condition. If so, slavecontroller 102 proceeds to step S160 to determine whether the last fuelcell cartridge 14 has been indexed. Otherwise, slave controller 102proceeds to step S144 to determine whether a voltage of any of the fuelcells of a currently indexed fuel cell cartridge 14 have an unacceptablevoltage condition (e.g., low voltage). If so, slave controller 102increments a low voltage counter at step S146. Next, slave controller102 proceeds to step S148 to determine whether the low voltage counteris at a maximum value. The maximum value is selected to provide theunacceptable fuel cell with a chance to recover and provide anacceptable voltage during a subsequent pass through the flow chart. Ifthe low voltage counter is at maximum, slave controller 102 proceeds tostep S150 to set the currently indexed fuel cell cartridge 14 status asdeactivated (e.g., down or off-line). Slave controller 102 instructsmaster controller 100 to shut off fuel to the currently indexed fuelcell cartridge 14 at step S152. Master controller 100 thereafterinstructs auxiliary valve slave controller 104 to shut off fuel to therespective fuel cell cartridge 14. At step S154, master controller 100additionally outputs a command to shunt slave controller 118 to shuntthe appropriate fuel cell cartridge 14. Also, master controller 100 canoutput the message to interface slave controller 108 to convey thestatus of the currently indexed fuel cell cartridge 14 using operatorinterface 16.

[0138] If the currently indexed fuel cell cartridge 14 has a propervoltage as determined at step S144, slave controller 102 proceeds tostep S145 to clear the low voltage counter. Slave controller 102associates the fuel cells with respective low voltage counter values.The low voltage counter for a given fuel cell previously determined tobe unacceptable during the current pass through the flow chart iscleared at step S145 if the voltage is deemed acceptable at step S144.

[0139] Slave controller 102 proceeds to step S156 to post high and lowvoltages of the fuel cells of the currently indexed fuel cell cartridge14 to memory. At step S158, slave controller 102 outputs the high andlow voltage information of the fuel cells of the fuel cell cartridge 14to master controller 100. Master controller 100 processes the high andlow voltages for the fuel cell cartridge 14 and can instruct interfaceslave controller 108 to display or otherwise convey the voltages to anoperator using operator interface 16.

[0140] At step S160, slave controller 102 determines whether the lastfuel cell cartridge 14 has been indexed. If not, slave controller 102indexes to a next fuel cell cartridge 14 at step S162 and thereafterreturns to step S142. If the last fuel cell cartridge 14 has beenindexed at step S160, slave controller 102 proceeds to step S164 todetermine whether too many fuel cell cartridges 14 are down (e.g., lessthan seven fuel cell cartridges 14 are down or off-line). If so, slavecontroller 102 sends an appropriate message to master controller 100 atstep S166.

[0141] At step S168, slave controller 102 monitors for the reception ofmessages from master controller 100. If a message is received, slavecontroller 102 processes the incoming message at step S170. At stepS172, slave controller 102 can transmit fuel cell data and any messages.Thereafter, slave controller 102 returns to step S120 to index the firstfuel cell 90 to repeat the analysis.

[0142] Referring to FIGS. 20-20A, a flow chart illustrating exemplaryoperations of auxiliary valve slave controller 104 is shown. Initially,slave controller 104 performs a communication check at step S180 toassure proper communications with master controller 100. At step S182,slave controller 104 listens for a start-up signal from mastercontroller 100. At step S184, it is determined whether the appropriatestart-up signal has been received. Once the start-up signal is received,slave controller 104 instructs auxiliary solenoids 44 to open respectiveauxiliary valves 45 at step S186. At step S188, slave controller 104commences to perform a bleed procedure wherein slave controller 104instructs bleed solenoid 42 to open bleed valve 43 for a defined lengthof time.

[0143] At step S190, slave controller 104 reads data and messages frommaster controller 100. Slave controller 104 determines whether themaster is off-line at step S192. If so, slave controller 104 closesauxiliary valves 45 at step S194. Otherwise, slave controller 104proceeds to step S196 to determine whether a shut down request has beenissued by master controller 100. If so, slave controller 104 proceeds tostep S194. Otherwise, slave controller 104 proceeds to step S198 todetermine whether a change in status of any fuel cell cartridges 14 hasbeen made. If so, slave controller 104 controls respective auxiliaryvalves 45 at step S200 to either supply fuel if the corresponding fuelcell cartridge 14 is on-line, or cease supply of fuel if the fuel cellcartridge 14 has been taken off-line.

[0144] At step S202, slave controller 104 monitors to determine whetherit is time for a bleed cycle. Slave controller 104 can be configured toperiodically implement a bleed cycle using bleed solenoid 42 and bleedvalve 43 according to a bleed timer. If it is time for a bleed cycle,slave controller 104 proceeds to step S204 to reset the bleed timer andthereafter commence a bleed procedure at step S206. As shown, slavecontroller 104 cycles back to step S190 to read any new data from mastercontroller 100.

[0145] Referring to FIGS. 21-21A, a flow chart illustrating exemplaryoperations of fan slave controller 106 is illustrated. Slave controller106 initially proceeds to step S210 and performs a communications checkto verify proper communications with master controller 100. At stepS212, slave controller 106 listens for an appropriate fan start-upsignal from master controller 100.

[0146] Once the appropriate start-up signal is received as determined atstep S214, slave controller 106 proceeds to step S216 to start operationof fan 54 at a maximum air flow setting. Thereafter, slave controller106 reads fan status information from fan monitoring circuitry 49 atstep S218. At step S220, slave controller 106 determines whether fan 54is operating properly. If not, slave controller 106 issues a shut downrequest to master controller 100 at step S222.

[0147] Otherwise, slave controller 106 receives any updated fan settingfrom master controller 100 at step S224. At step S226, slave controller106 can output appropriate signals to fan control circuitry 48 to adjustthe operation of fan 54. At step S228, slave controller 106 determineswhether a shut down command has been issued by master controller 100. Ifnot, slave controller 106 returns to step S218 to read the status of fan54. Otherwise, slave controller 106 proceeds to step S230 to shut offfan 54.

[0148] Referring to FIG. 22, a flow chart illustrating exemplaryoperations of interface slave controller 108 is shown. Initially, slavecontroller 108 proceeds to step S240 to perform a communications checkwith master controller 100. Thereafter, slave controller 108 outputsappropriate message information to operator interface 16 for conveyanceto an operator. In the described embodiment, operator interface 16displays the message information received from master controller 100.

[0149] Slave controller 108 listens for updates to operator interface 16at step S244. At step S246, it is determined whether master controller100 is off-line. If so, slave controller 108 sends an error message tooperator interface 16 to indicate master controller 100 is off-line.Otherwise, slave controller 108 proceeds to step S250 to determinewhether there was a change in the status of operator interface 16. Ifnot, slave controller 108 proceeds to step S244 and listens for updatesfor operator interface 16. If a change in interface status is indicatedat step S250, slave controller 108 proceeds to step S252 to updateoperator interface 16.

[0150] Referring to FIG. 23, a flow chart illustrating exemplaryoperations of external port slave controller 110 is illustrated.Initially, slave controller 110 performs a communications check withmaster controller 100 at step S260. Thereafter, slave controller 100reads any input communication from remote device 24 and communicationport 36. At step S264, slave controller 110 sends any receivedcommunications to master controller 100. At step S266, slave controller110 receives any communications from master controller 100. Slavecontroller 110 proceeds to forward any communications to communicationport 36 and remote device 24 at step S268.

[0151] Referring to FIGS. 24-24A, a flow chart illustrating exemplaryoperations of system slave controller 112 is shown. Initially, at stepS270, slave controller 112 performs a communications check with mastercontroller 100. Next, slave controller 112 can read status informationfrom power supply sensors 31 and current sensor 40 at step S272. At stepS274, it is determined by slave controller 112 whether the inputtedstatus values are within appropriate ranges. If not, slave controller112 can generate an error message at step S276 for application to mastercontroller 100.

[0152] Otherwise, slave controller 112 proceeds to step S278 and listensfor a main valve open command from master controller 100. At a stepS280, it is determined whether the open valve command was received. Oncethe open valve command is received, slave controller 112 proceeds tostep S282 to activate main valve 47 using main solenoid 46. At stepS284, slave controller 112 listens for a shut down command from mastercontroller 100.

[0153] Proceeding to step S286, slave controller 112 determines whetherthe master controller 100 is off-line. If so, slave controller 112proceeds to step S296 to shut off power supply 32 and main valve 47using main solenoid 46. If master controller 100 is on-line, slavecontroller 112 proceeds to step S288 to again read status values frompower supply sensors 31 and current sensor 40. Slave controller 112 cancontrol charge circuitry 34 to charge battery 35, if necessary, at stepS290 responsive to the values read at step S288.

[0154] At step S292, slave controller 112 determines whether the valuesare within the appropriate ranges. If not, slave controller 112 proceedsto step S294 to generate an error message for application to mastercontroller 100. Otherwise, at step S296, slave controller 112 monitorsfor the presence of a shut down command or request from mastercontroller 100. If no shut down command is issued, slave controller 112returns to step S284. If a shut down request or command is received atstep S296, slave controller 112 proceeds to step S296 to shut off mainvalve 47 using main solenoid 46 as well as turn off power supply 32.

[0155] Referring to FIG. 25, a flow chart illustrating exemplaryoperations of sensor slave controller 114 is shown. Initially, at stepS300, slave controller 114 performs a communication check with mastercontroller 100. At step S302, slave controller 114 controls heaters 74,75, if necessary, to bring associated fuel sensors 58, 61 within properoperating temperature ranges. Thereafter, slave controller 114 isconfigured to read information from fuel detection circuitry 64 andcorresponding fuel sensors 58, 61.

[0156] Responsive to reading the fuel sensor values, slave controller114 determines at step S306 whether a major leak was detected. If so,slave controller 114 forwards an appropriate major leak message tomaster controller 100 at step S308: At step S310, the fuel sensor valuesare analyzed to determine whether a minor leak was detected. If so,slave controller 114 sends an appropriate minor leak message to mastercontroller 100 at step S312.

[0157] At step S314, slave controller 114 reads external temperatureinformation from temperature circuitry 67 and associated temperaturesensor 59. At step S316, slave controller 114 sends external temperaturevalues to master controller 100.

[0158] Referring to FIG. 26, a flow chart illustrating exemplaryoperations of air temperature slave controller 116 is shown. Initially,slave controller 116 performs a communication check with mastercontroller 100 at step S320. Thereafter, slave controller 116 readstemperature values from temperature circuitry 68 and associatedtemperature sensor 55 located within air plenum 51. At step S324, slavecontroller 116 reads a temperature set point as calculated from mastercontroller 100.

[0159] At step S326, slave controller 116 sets recirculation using airpassage 56 and fan 54 to maintain a set point temperature. Slavecontroller 116 outputs the air temperature of plenum 51 as determined bytemperature sensor 55 to master controller 100 at step S328.

[0160] Referring to FIG. 27, a flow chart illustrating exemplaryoperations of shunt slave controller 118 is shown. Initially, at stepS330, slave controller 118 performs a communication check with mastercontroller 100. At step S332, slave controller 118 reads data frommaster controller 100.

[0161] At step S334, it is determined whether there was a change instatus of the fuel cell cartridges 14. If so, slave controller 118proceeds to step S336 to determine whether there is a change of any ofthe fuel cell cartridges 14 to an off-line condition. If not, theappropriate switching device 96 for the respective fuel cell cartridge14 is latched to an off position at step S338. Alternatively, slavecontroller 118 proceeds to step S340 to latch the appropriate switchingdevice 96 for the respective fuel cell cartridge 14 in an on position.

[0162] Following processing of steps S338 or S340, or alternatively ifthere is no change in status of fuel cell cartridges 14 as determined atstep S334, slave controller 118 proceeds to step S342 to cyclicallyshunt fuel cells 90 within fuel cell cartridges 14 as described indetail in U.S. patent application Ser. No. 09/108,667 incorporated byreference above.

[0163] Referring to FIG. 28, a flow chart illustrating exemplaryoperations of switch slave controller 120 is shown. Slave controller 120performs a communication check with master controller 100 at step S350.Thereafter, slave controller 120 reads switch status information fromswitches 20 and switch conditioning circuitry 19 at step S352. At stepS354, slave controller 120 reads load enable status information frommaster controller 100.

[0164] Slave controller 120 determines whether a power off request wasreceived from master controller 100 at step S356. If yes, slavecontroller 120 proceeds to step S358 to send a shut down message tomaster controller 100. Otherwise, slave controller 120 proceeds to stepS360. Slave controller 120 determines whether a load enable request wasprovided from switches 20. If so, slave controller 120 proceeds to stepS362 to determine whether master controller 100 has indicated fuel cellpower system 10 is ready to provide power as determined in step S354. Ifso, slave controller 120 proceeds to step S364 to enable switchingdevice 38.

[0165] At step S366, slave controller 120 determines whether the mastercontroller 100 is in an off-line condition. If so, slave controller 120disables switching device 38 at step S368. Otherwise, slave controller120 proceeds to step S370 to determine whether a cartridge reset hasbeen indicated from switches 20. If so, slave controller 120 proceeds tosend a cartridge reset message to master controller 100 at step S372.Slave controller 120 then returns to step S352 to read switch statusfrom switch conditioning circuitry 19 and associated switches 20 at stepS352.

[0166] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A fuel cell power system comprising: a plurality of fuel cellselectrically coupled with plural terminals and individually configuredto convert chemical energy into electricity; and a digital controlsystem configured to at least one of control and monitor an operation ofthe fuel cells.
 2. The fuel cell power system according to claim 1wherein the control system is configured to control the operation. 3.The fuel cell power system according to claim 1 wherein the controlsystem is configured to monitor the operation.
 4. The fuel cell powersystem according to claim 1 wherein the fuel cells are coupled inseries.
 5. The fuel cell power system according to claim 1 wherein thecontrol system comprises a plurality of distributed controllers.
 6. Thefuel cell power system according to claim 5 wherein the distributedcontrollers are configured in a master-slave relationship.
 7. The fuelcell power system according to claim 1 wherein the fuel cells comprisepolymer electrolyte membrane fuel cells.
 8. The fuel cell power systemaccording to claim 1 wherein the fuel cells are configured to beindividually selectively deactivated and remaining ones of the fuelcells are configured to provide electricity to the terminals with othersof the fuel cells deactivated.
 9. The fuel cell power system accordingto claim 8 wherein the fuel cells are individually configured to bephysically removable.
 10. The fuel cell power system according to claim8 wherein the fuel cells are individually configured to be electricallybypassed.
 11. The fuel cell power system according to claim 1 furthercomprising a plurality of switching devices configured to selectivelyshunt respective fuel cells.
 12. The fuel cell power system according toclaim 11 wherein the control system is configured to monitor at leastone electrical characteristic of the fuel cells and to control theswitching devices responsive to the monitoring.
 13. The fuel cell powersystem according to claim 1 further comprising: a housing about the fuelcells; a temperature sensor within the housing; and an air temperaturecontrol assembly configured to at least one of increase and decrease thetemperature in the housing.
 14. The fuel cell power system according toclaim 13 wherein the control system is configured to monitor temperatureusing the temperature sensor and to control the air temperature controlassembly responsive to the monitoring to maintain the temperature withinthe housing within a predefined range.
 15. The fuel cell power systemaccording to claim 13 wherein the control system is configured tomonitor temperature using the temperature sensor and to control the airtemperature control assembly responsive to the monitoring to maintainthe temperature within the housing within a predefined range ofapproximately 25° Celsius to 80° Celsius.
 16. The fuel cell power systemaccording to claim 1 further comprising a fan configured to direct airto the fuel cells, and the control system is configured to control thefan.
 17. The fuel cell power system according to claim 1 furthercomprising a plurality of valves configured to supply fuel to respectivefuel cells, and the control system is configured to control the valves.18. The fuel cell power system according to claim 1 further comprising amain valve configured to supply fuel to the fuel cells, and the controlsystem is configured to control the main valve.
 19. The fuel cell powersystem according to claim 1 further comprising a communication portadapted to couple with a remote device, and the control system isconfigured to communicate with the remote device via the communicationport.
 20. The fuel cell power system according to claim 19 wherein theshut down operation deactivates one or more of the fuel cells.
 21. Thefuel cell power system according to claim 19 wherein the shut downoperation deactivates all the fuel cells.
 22. The fuel cell power systemaccording to claim 1 further comprising a switching device intermediateone of the terminals and the fuel cells, and the control system isconfigured to control the switching device.
 23. The fuel cell powersystem according to claim 1 further comprising: a housing about the fuelcells; and a fuel sensor configured to monitor for the presence of fuelwithin the housing, and the control system is coupled with the fuelsensor and configured to implement a shut down operation responsive to adetection of fuel within the housing.
 24. The fuel cell power systemaccording to claim 1 wherein the fuel cells are provided in a pluralityof cartridges.
 25. A fuel cell power system comprising: a housing; aplurality of terminals; a plurality of fuel cells within the housing andelectrically coupled with the terminals and configured to convertchemical energy into electricity; a plurality of valves adapted tocouple with a fuel source and configured to selectively supply fuel torespective fuel cells; and a control system configured to control theplurality of valves.
 26. The fuel cell power system according to claim25 wherein the control system comprises a plurality of distributedcontrollers.
 27. The fuel cell power system according to claim 25wherein the fuel cells comprise polymer electrolyte membrane fuel cells.28. The fuel cell power system according to claim 25 wherein the fuelcells are configured to be individually selectively deactivated andremaining ones of the fuel cells are configured to provide electricityto the terminals with others of the fuel cells deactivated.
 29. The fuelcell power system according to claim 28 wherein the fuel cells areindividually configured to be physically removable.
 30. The fuel cellpower system according to claim 28 wherein the fuel cells areindividually configured to be electrically bypassed.
 31. The fuel cellpower system according to claim 25 wherein the control system isconfigured to monitor at least one electrical characteristic of the fuelcells and to control the respective valves responsive to the monitoring.32. A fuel cell power system comprising: a housing; a plurality ofterminals; at least one fuel cell within the housing and electricallycoupled with the terminals and configured to convert chemical energyinto electricity; a bleed valve configured to selectively purge matterfrom the at least one fuel cell; and a control system configured tocontrol selective positioning of the bleed valve.
 33. The fuel cellpower system according to claim 32 wherein the control system comprisesa plurality of distributed controllers.
 34. The fuel cell power systemaccording to claim 32 wherein the at least one fuel cell comprises aplurality of polymer electrolyte membrane fuel cells.
 35. The fuel cellpower system according to claim 32 wherein the at least one fuel cellcomprises a plurality of fuel cells.
 36. The fuel cell power systemaccording to claim 35 wherein the fuel cells are configured to beindividually selectively deactivated and remaining ones of the fuelcells are configured to provide electricity to the terminals with othersof the fuel cells deactivated.
 37. The fuel cell power system accordingto claim 32 wherein the control system is configured to periodicallyopen the bleed valve.
 38. The fuel cell power system according to claim32 further comprising a connection arranged to provide drainage from ananode side of the at least one fuel cell to the bleed valve.
 39. A fuelcell power system comprising: a housing; a plurality of terminals; atleast one fuel cell within the housing and electrically coupled with theterminals and configured to convert chemical energy into electricity; afan within the housing and configured to direct air to the at least onefuel cell; and a control system configured to control an operation ofthe fan.
 40. The fuel cell power system according to claim 39 whereinthe control system comprises a plurality of distributed controllers. 41.The fuel cell power system according to claim 39 wherein the at leastone fuel cell comprises a plurality of polymer electrolyte membrane fuelcells.
 42. The fuel cell power system according to claim 39 wherein theat least one fuel cell comprises a plurality of fuel cells.
 43. The fuelcell power system according to claim 42 wherein the fuel cells areconfigured to be individually selectively deactivated and remaining onesof the fuel cells are configured to provide electricity to the terminalswith others of the fuel cells deactivated.
 44. The fuel cell powersystem according to claim 39 further comprising at least one sensorconfigured to at least one of monitor current supplied to a load coupledwith the terminals and monitor voltage of the at least one fuel cell,and the control system is configured to control a rate of air flow ofthe fan responsive to the monitoring.
 45. The fuel cell power systemaccording to claim 39 wherein the at least one fuel cell includes acathode side and the fan and the housing are configured to direct airinto the cathode side of the at least one fuel cell.
 46. The fuel cellpower system according to claim 39 further comprising a plenum withinthe housing and configured to direct air from the fan to the at leastone fuel cell.
 47. The fuel cell power system according to claim 46wherein the plenum is configured to direct air to a cathode side of theat least one fuel cell.
 48. The fuel cell power system according toclaim 39 further comprising an air flow device configured to operateresponsive to control from the control system to permit selectivepassage of air at least one of into and out of the housing.
 49. The fuelcell power system according to claim 39 further comprising monitoringcircuitry configured to monitor an air flow rate of the fan and output asignal indicative of the air flow rate to the control system.
 50. Thefuel cell power system according to claim 49 wherein the control systemis configured to control an air flow rate of the fan.
 51. A fuel cellpower system comprising: a housing; a plurality of terminals; at leastone fuel cell within the housing and electrically coupled with theterminals and configured to convert chemical energy into electricity; acontrol system configured to at least one of control and monitor anoperation of the at least one fuel cell; and an operator interfacecoupled with the control system to indicate at least one operationalstatus responsive to control from the control system.
 52. The fuel cellpower system according to claim 51 wherein the control system comprisesa plurality of distributed controllers.
 53. The fuel cell power systemaccording to claim 51 wherein the at least one fuel cell comprises aplurality of polymer electrolyte membrane fuel cells.
 54. The fuel cellpower system according to claim 51 wherein the at least one fuel cellcomprises a plurality of fuel cells.
 55. The fuel cell power systemaccording to claim 54 wherein the fuel cells are configured to beindividually selectively deactivated and remaining ones of the fuelcells are configured to provide electricity to the terminals with othersof the fuel cells deactivated.
 56. The fuel cell power system accordingto claim 51 wherein the operator interface is positioned for observationfrom the exterior of the housing.
 57. The fuel cell power systemaccording to claim 51 wherein the operator interface comprises a displayconfigured to emit a human perceptible signal.
 58. The fuel cell powersystem according to claim 51 wherein the operator interface comprisesinterface switches configured to receive operator inputs.
 59. A fuelcell power system comprising: a plurality of terminals; at least onefuel cell electrically coupled with the terminals and configured toconvert chemical energy into electricity; a power supply configured toselectively supply electricity; and a control system configured tomonitor at least one operational condition of the power supply.
 60. Thefuel cell power system according to claim 59 wherein the control systemcomprises a plurality of distributed controllers.
 61. The fuel cellpower system according to claim 59 wherein the at least one fuel cellcomprises a plurality of polymer electrolyte membrane fuel cells. 62.The fuel cell power system according to claim 59 wherein the at leastone fuel cell comprises a plurality of fuel cells.
 63. The fuel cellpower system according to claim 62 wherein the fuel cells are configuredto be individually selectively deactivated and remaining ones of thefuel cells are configured to provide electricity to the terminals withothers of the fuel cells deactivated.
 64. The fuel cell power systemaccording to claim 59 wherein the power supply supplies electricity tothe control system.
 65. The fuel cell power system according to claim 59wherein the power supply includes a battery.
 66. The fuel cell powersystem according to claim 65 further comprising charge circuitryconfigured to selectively charge the battery responsive to control fromthe control system.
 67. The fuel cell power system according to claim 59further comprising an operator interface and the control system isconfigured to control the operator interface to indicate the at leastone operational condition.
 68. A fuel cell power system comprising: aplurality of terminals; at least one fuel cell electrically coupled withthe terminals and configured to convert chemical energy intoelectricity; a sensor configured to monitor at least one electricalcondition of the at least one fuel cell; and a control system coupledwith the sensor and configured to monitor the sensor.
 69. The fuel cellpower system according to claim 68 wherein the control system comprisesa plurality of distributed controllers.
 70. The fuel cell power systemaccording to claim 68 wherein the at least one fuel cell comprises aplurality of polymer electrolyte membrane fuel cells.
 71. The fuel cellpower system according to claim 68 wherein the at least one fuel cellcomprises a plurality of fuel cells.
 72. The fuel cell power systemaccording to claim 71 wherein the fuel cells are configured to beindividually selectively deactivated and remaining ones of the fuelcells are configured to provide electricity to the terminals with othersof the fuel cells deactivated.
 73. The fuel cell power system accordingto claim 68 further comprising an operator interface and the controlsystem is configured to control the operator interface to indicate theat least one electrical condition.
 74. The fuel cell power systemaccording to claim 68 further comprising a fan configured to direct airto the at least one fuel cell and the control system is configured tocontrol the fan responsive to the at least one electrical condition. 75.A fuel cell power system comprising: a plurality of terminals; aplurality of fuel cells electrically coupled with the terminals andconfigured to convert chemical energy into electricity; a main valveadapted to couple with a fuel source and configured to selectivelysupply fuel to the fuel cells; and a control system configured tocontrol the main valve.
 76. The fuel cell power system according toclaim 75 wherein the control system comprises a plurality of distributedcontrollers.
 77. The fuel cell power system according to claim 75wherein the fuel cells comprise polymer electrolyte membrane fuel cells.78. The fuel cell power system according to claim 75 wherein the fuelcells are configured to be individually selectively deactivated andremaining ones of the fuel cells are configured to provide electricityto the terminals with others of the fuel cells deactivated.
 79. The fuelcell power system according to claim 75 further comprising a pluralityof auxiliary valves configured to selectively supply fuel to respectivefuel cells.
 80. A fuel cell power system comprising: a housing; aplurality of terminals; at least one fuel cell within the housing andelectrically coupled with the terminals and configured to convertchemical energy into electricity; an air temperature control assemblyconfigured to direct air within the housing to the at least one fuelcell and comprising a modifying element configured to condition thetemperature of the air; and a control system configured to control themodifying element.
 81. The fuel cell power system according to claim 80wherein the control system comprises a plurality of distributedcontrollers.
 82. The fuel cell power system according to claim 80wherein the at least one fuel cell comprises a plurality of polymerelectrolyte membrane fuel cells.
 83. The fuel cell power systemaccording to claim 80 wherein the at least one fuel cell comprises aplurality of fuel cells.
 84. The fuel cell power system according toclaim 83 wherein the fuel cells are configured to be individuallyselectively deactivated and remaining ones of the fuel cells areconfigured to provide electricity to the terminals with others of thefuel cells deactivated.
 85. The fuel cell power system according toclaim 80 further comprising a temperature sensor configured to monitorthe temperature of the directed air within the housing.
 86. The fuelcell power system according to claim 85 wherein the control system isconfigured to monitor the temperature of the directed air from thetemperature sensor and to control the modifying element responsive tothe monitoring of the temperature.
 87. The fuel cell power systemaccording to claim 80 wherein the modifying element comprises a heater.88. A fuel cell power system comprising: a housing; a plurality ofterminals; at least one fuel cell within the housing and electricallycoupled with the terminals and configured to convert chemical energyinto electricity; a fuel delivery system configured to supply fuel tothe at least one fuel cell; a fuel sensor positioned within the housing;and a control system configured to monitor a detection of fuel withinthe housing using the fuel detection sensor.
 89. The fuel cell powersystem according to claim 88 wherein the control system comprises aplurality of distributed controllers.
 90. The fuel cell power systemaccording to claim 88 wherein the at least one fuel cell comprises aplurality of polymer electrolyte membrane fuel cells.
 91. The fuel cellpower system according to claim 88 wherein the at least one fuel cellcomprises a plurality of fuel cells.
 92. The fuel cell power systemaccording to claim 91 wherein the fuel cells are configured to beindividually selectively deactivated and remaining ones of the fuelcells are configured to provide electricity to the terminals with othersof the fuel cells deactivated.
 93. The fuel cell power system accordingto claim 88 further comprising an operator interface and the controlsystem is configured to control the operator interface to indicate adetection of fuel.
 94. The fuel cell power system according to claim 88wherein the fuel sensor comprises a hydrogen gas sensor.
 95. The fuelcell power system according to claim 88 wherein the at least one fuelcell comprises a plurality of fuel cells, and the fuel delivery systemcomprises a plurality of valves configured supply fuel to respectiveones of the fuel cells.
 96. The fuel cell power system according toclaim 95 wherein the control system is configured to selectively closethe valves responsive to a detection of fuel using the fuel sensor. 97.The fuel cell power system according to claim 88 further comprising aheater configured to selectively impart heat flux to the fuel sensor.98. A fuel cell power system comprising: a housing; a plurality ofterminals; at least one fuel cell within the housing and electricallycoupled with the terminals and configured to convert chemical energyinto electricity; a temperature sensor within the housing; and a controlsystem coupled with the temperature sensor and configured to monitor thetemperature in the housing using the temperature sensor.
 99. The fuelcell power system according to claim 98 wherein the control systemcomprises a plurality of distributed controllers.
 100. The fuel cellpower system according to claim 98 wherein the at least one fuel cellcomprises a plurality of polymer electrolyte membrane fuel cells. 101.The fuel cell power system according to claim 98 wherein the at leastone fuel cell comprises a plurality of fuel cells.
 102. The fuel cellpower system according to claim 101 wherein the fuel cells areconfigured to be individually selectively deactivated and remaining onesof the fuel cells are configured to provide electricity to the terminalswith others of the fuel cells deactivated.
 103. The fuel cell powersystem according to claim 98 further comprising an air temperaturecontrol assembly configured to at least one of increase and decrease thetemperature in the housing.
 104. The fuel cell power system according toclaim 103 wherein the control system is configured to control the airtemperature control assembly.
 105. The fuel cell power system accordingto claim 103 wherein the control system is configured to control the airtemperature control assembly to maintain the temperature in the housingwithin a predefined range.
 106. The fuel cell power system according toclaim 103 wherein the control system is configured to control the airtemperature control assembly to maintain the temperature in the housingwithin a predefined range of approximately 25° Celsius to 80° Celsius.107. The fuel cell power system according to claim 103 wherein the airtemperature control assembly comprises: a fan configured to circulateair within the housing; and an air flow device configured to permitselective passage of air at least one of into and out of the housing.108. The fuel cell power system according to claim 107 wherein thecontrol system is configured to control the fan and the air flow device.109. The fuel cell power system according to claim 98 further comprisinga temperature sensor configured to monitor a temperature exterior of thehousing.
 110. A fuel cell power system comprising: a plurality ofterminals; at least one fuel cell within the housing and electricallycoupled with the terminals and configured to convert chemical energyinto electricity; at least one switching device configured toselectively shunt the at least one fuel cell; and a control systemconfigured to control the at least one switching device.
 111. The fuelcell power system according to claim 110 wherein the control systemcomprises a plurality of distributed controllers.
 112. The fuel cellpower system according to claim 110 wherein the at least one fuel cellcomprises a plurality of polymer electrolyte membrane fuel cells. 113.The fuel cell power system according to claim 110 wherein the at leastone fuel cell comprises a plurality of fuel cells.
 114. The fuel cellpower system according to claim 113 wherein the fuel cells areconfigured to be individually selectively deactivated and remaining onesof the fuel cells are configured to provide electricity to the terminalswith others of the fuel cells deactivated.
 115. The fuel cell powersystem according to claim 110 wherein the control system is configuredto shunt the at least one fuel cell for a variable period of time. 116.The fuel cell power system according to claim 110 wherein the at leastone fuel cell comprises plural fuel cells and the at least one switchingdevice comprises plural switching devices.
 117. The fuel cell powersystem according to claim 116 wherein the control system is configuredto sequentially shunt the fuel cells using the respective switchingdevices.
 118. The fuel cell power system according to claim 116 whereinthe control system is configured to shunt individual ones of the fuelcells using the respective switching devices.
 119. The fuel cell powersystem according to claim 116 wherein the control system is configuredto shunt the individual ones of the fuel cells according to a specifiedorder.
 120. The fuel cell power system according to claim 116 furthercomprising a plurality of valves individually configured to selectivelysupply fuel to respective fuel cells, and wherein the control system isconfigured to control the valves.
 121. The fuel cell power systemaccording to claim 120 wherein the control system is configured to ceasesupply of fuel to shunted fuel cells using respective ones of thevalves.
 122. The fuel cell power system according to claim 116 whereinthe switching devices comprise MOSFET switching devices.
 123. A fuelcell power system comprising: a housing; a plurality of terminals; atleast one fuel cell within the housing and electrically coupled with theterminals and configured to convert chemical energy into electricity; aswitching device coupled intermediate the at least one fuel cell and oneof the terminals; and a control system coupled with the switching deviceand configured to control the switching device to selectively couple theterminal with the at least one fuel cell.
 124. The fuel cell powersystem according to claim 123 wherein the control system comprises aplurality of distributed controllers.
 125. The fuel cell power systemaccording to claim 123 wherein the at least one fuel cell comprises aplurality of polymer electrolyte membrane fuel cells.
 126. The fuel cellpower system according to claim 123 wherein the at least one fuel cellcomprises a plurality of fuel cells.
 127. The fuel cell power systemaccording to claim 126 wherein the fuel cells are configured to beindividually selectively deactivated and remaining ones of the fuelcells are configured to provide electricity to the terminals with othersof the fuel cells deactivated.
 128. The fuel cell power system accordingto claim 123 wherein the switching device comprises at least one MOSFETswitching device.
 129. The fuel cell power system according to claim 123further comprising a temperature sensor positioned within the housing,and the control system is configured to monitor the temperature withinthe housing and to couple the terminal with the at least one fuel cellusing the switching device responsive to the temperature being within apredefined range.
 130. A method of controlling a fuel cell power systemcomprising: providing a plurality of fuel cells individually configuredto convert chemical energy into electricity; electrically coupling theplurality of fuel cells; providing a first terminal coupled with thefuel cells; providing a second terminal coupled with the fuel cells; andcoupling a digital control system with the fuel cells to at least one ofmonitor and control an operation of the fuel cells.
 131. The methodaccording to claim 130 further comprising monitoring the operation ofthe fuel cells.
 132. The method according to claim 130 furthercomprising controlling the operation of the fuel cells.
 133. The methodaccording to claim 130 wherein the coupling the control system comprisescoupling a plurality of distributed controllers.
 134. The methodaccording to claim 130 wherein the providing the fuel cells comprisesproviding polymer electrolyte membrane fuel cells.
 135. The methodaccording to claim 134 further comprising deactivating at least one ofthe fuel cells.
 136. The method according to claim 135 wherein thedeactivating comprises physically removing.
 137. The method according toclaim 135 wherein the deactivating comprises electrically bypassing.138. The method according to claim 135 further comprising providingelectricity to a load coupled with the terminals with the at least onefuel cell deactivated.
 139. The method according to claim 130 furthercomprising selectively shunting at least one of the fuel cells.
 140. Themethod according to claim 130 further comprising: monitoring at leastone electrical characteristic of the fuel cells; and shunting at leastone of the fuel cells responsive to the monitoring.
 141. The methodaccording to claim 130 further comprising maintaining an air temperatureabout the fuel cells in a predefined range.
 142. The method according toclaim 130 further comprising maintaining an air temperature about thefuel cells in a predefined range of approximately 25° Celsius to 80°Celsius.
 143. The method according to claim 130 further comprisingdirecting air to the fuel cells using a fan.
 144. The method accordingto claim 143 further comprising: monitoring a load coupled with theterminals; and controlling the fan responsive to the monitoring usingthe control system.
 145. The method according to claim 130 furthercomprising: supplying fuel to the fuel cells using a plurality ofauxiliary valves; and controlling the auxiliary valves using the controlsystem.
 146. The method according to claim 145 further comprising:supplying fuel to the auxiliary valves using a main valve; andcontrolling the main valve using the control system.
 147. The methodaccording to claim 130 further comprising: communicating with a remotedevice using a communication port; and controlling the communicatingusing the control system.
 148. The method according to claim 130 furthercomprising: switching a connection intermediate one of the terminals andthe fuel cells; and controlling the switching using the control system.149. The method according to claim 130 further comprising: monitoringfor the presence of fuel within a housing about the fuel cells; andimplementing a shut down operation responsive to the monitoring usingthe control system.
 150. The method according to claim 149 wherein theimplementing deactivates one or more of the fuel cells.
 151. The methodaccording to claim 149 wherein the implementing deactivates all of thefuel cells.
 152. A method of controlling a fuel cell power systemcomprising: providing at least one fuel cell configured to convertchemical energy into electricity; providing a first terminal coupledwith the at least one fuel cell; providing a second terminal coupledwith the at least one fuel cell; supplying fuel to the at least one fuelcell; and controlling the supplying using a control system.
 153. Themethod according to claim 152 wherein the controlling comprisescontrolling using the control system comprising a plurality ofdistributed controllers.
 154. The method according to claim 152 whereinthe providing the at least one fuel cell comprises providing the atleast one fuel cell having a plurality of polymer electrolyte membranefuel cells.
 155. The method according to claim 152 wherein the providingthe at least one fuel cell comprises providing a plurality of fuelcells.
 156. The method according to claim 155 further comprisingdeactivating at least one of the fuel cells.
 157. The method accordingto claim 156 further comprising providing electricity to a load coupledwith the terminals with the at least one fuel cell deactivated.
 158. Themethod according to claim 152 further comprising monitoring at least oneelectrical characteristic of the at least one fuel cell, and thecontrolling is responsive to the monitoring.
 159. A method ofcontrolling a fuel cell power system comprising: providing at least onefuel cell configured to convert chemical energy into electricity;providing a first terminal coupled with the at least one fuel cell;providing a second terminal coupled with the at least one fuel cell;selectively exhausting a connection coupled with the at least one fuelcell; and controlling the exhausting using a control system.
 160. Themethod according to claim 159 wherein the controlling comprisescontrolling using the control system comprising a plurality ofdistributed controllers.
 161. The method according to claim 159 whereinthe providing the at least one fuel cell comprises providing the atleast one fuel cell having a plurality of polymer electrolyte membranefuel cells.
 162. The method according to claim 159 wherein the providingthe at least one fuel cell comprises providing a plurality of fuelcells.
 163. The method according to claim 162 further comprisingdeactivating at least one of the fuel cells.
 164. The method accordingto claim 163 further comprising providing electricity to a load coupledwith the terminals with the at least one fuel cell deactivated.
 165. Themethod according to claim 159 wherein the selectively exhaustingcomprises periodically exhausting responsive to control of the controlsystem.
 166. The method according to claim 159 wherein the exhaustingcomprises exhausting using a bleed valve.
 167. The method according toclaim 159 wherein the exhausting comprises exhausting from an anode ofthe at least one fuel cell.
 168. A method of controlling a fuel cellpower system comprising: providing at least one fuel cell configured toconvert chemical energy into electricity; providing a first terminalcoupled with the at least one fuel cell; providing a second terminalcoupled with the at least one fuel cell; directing air to the at leastone fuel cell; and controlling the directing using a control system.169. The method according to claim 168 wherein the controlling comprisescontrolling using the control system comprising a plurality ofdistributed controllers.
 170. The method according to claim 168 whereinthe providing the at least one fuel cell comprises providing the atleast one fuel cell having a plurality of polymer electrolyte membranefuel cells.
 171. The method according to claim 168 wherein the providingthe at least one fuel cell comprises providing a plurality of fuelcells.
 172. The method according to claim 171 further comprisingdeactivating at least one of the fuel cells.
 173. The method accordingto claim 172 further comprising providing electricity to a load coupledwith the terminals with the at least one fuel cell deactivated.
 174. Themethod according to claim 168 further comprising providing electricityto a load coupled with the terminals, and the controlling is responsiveto the monitoring.
 175. The method according to claim 168 furthercomprising monitoring at least one of voltage of the at least one fuelcell and current passing through the at least one fuel cell, and thecontrolling is responsive to the monitoring.
 176. The method accordingto claim 168 wherein the directing comprises directing air into acathode side of the at least on fuel cell.
 177. The method according toclaim 176 wherein the directing comprises directing using a fan, and thecontrolling comprises controlling an air flow rate of the fan.
 178. Themethod according to claim 168 further comprising introducing exteriorair into a housing about the at least one fuel cell.
 179. The methodaccording to claim 168 further comprising monitoring the temperature ofthe air.
 180. The method according to claim 179 further comprisingcontrolling a modifying element using the control system to control thetemperature of the air responsive to the monitoring.
 181. A method ofcontrolling a fuel cell power system comprising: providing at least onefuel cell configured to convert chemical energy into electricity;providing a first terminal coupled with the at least one fuel cell;providing a second terminal coupled with the at least one fuel cell;indicating at least one operational status of the fuel cell power systemusing an operator interface; and controlling the indicating using acontrol system.
 182. The method according to claim 181 wherein thecontrolling comprises controlling using the control system comprising aplurality of distributed controllers.
 183. The method according to claim181 wherein the providing the at least one fuel cell comprises providingthe at least one fuel cell having a plurality of polymer electrolytemembrane fuel cells.
 184. The method according to claim 181 wherein theproviding the at least one fuel cell comprises providing a plurality offuel cells.
 185. The method according to claim 184 further comprisingdeactivating at least one of the fuel cells.
 186. The method accordingto claim 185 further comprising providing electricity to a load coupledwith the terminals with the at least one fuel cell deactivated.
 187. Themethod according to claim 181 wherein the indicating comprises emittinga human perceptible signal.
 188. The method according to claim 181wherein the indicating comprises indicating using a display.
 189. Themethod according to claim 181 further comprising forwarding the at leastone operational status to a remote device.
 190. The method according toclaim 181 further comprising is receiving operator inputs using theoperator interface.
 191. A method of controlling a fuel cell powersystem comprising: providing at least one fuel cell configured toconvert chemical energy into electricity; providing a first terminalcoupled with the at least one fuel cell; providing a second terminalcoupled with the at least one fuel cell; supplying electricity using apower supply; and monitoring at least one electrical condition of thepower supply using a control system.
 192. The method according to claim191 wherein the controlling comprises controlling using the controlsystem comprising a plurality of distributed controllers.
 193. Themethod according to claim 191 wherein the providing the at least onefuel cell comprises providing the fuel cell having a plurality ofpolymer electrolyte membrane fuel cells.
 194. The method according toclaim 191 wherein the providing the at least one fuel cell comprisesproviding a plurality of fuel cells.
 195. The method according to claim194 further comprising deactivating at least one of the fuel cells. 196.The method according to claim 195 further comprising providingelectricity to a load coupled with the terminals with the at least onefuel cell deactivated.
 197. The method according to claim 191 whereinthe supplying comprises supplying electricity to the control system.198. The method according to claim 191 wherein the supplying comprisessupplying power using the power supply comprising a battery.
 199. Themethod according to claim 198 further comprising: charging the battery;and controlling the charging using the control system.
 200. A method ofcontrolling a fuel cell power system comprising: providing at least onefuel cell configured to convert chemical energy into electricity;providing a first terminal coupled with the at least one fuel cell;providing a second terminal coupled with the at least one fuel cell; andmonitoring an electrical condition of the at least one fuel cell using acontrol system.
 201. The method according to claim 200 wherein thecontrolling comprises controlling using the control system comprising aplurality of distributed controllers.
 202. The method according to claim200 wherein the providing the at least one fuel cell comprises providingthe fuel cell having a plurality of polymer electrolyte membrane fuelcells.
 203. The method according to claim 200 wherein the providing theat least one fuel cell comprises providing a plurality of fuel cells.204. The method according to claim 203 further comprising deactivatingat least one of the fuel cells.
 205. The method according to claim 204further comprising providing electricity to a load coupled with theterminals with the at least one fuel cell deactivated.
 206. The methodaccording to claim 200 further comprising indicating the electricalcondition using an operator interface.
 207. The method according toclaim 200 further comprising: directing air to the at least one fuelcell; and controlling the directing using the control system responsiveto the monitoring.
 208. The method according to claim 200 furthercomprising shunting the at least one fuel cell after the monitoring.209. A method of controlling a fuel cell power system comprising:providing a plurality of fuel cells individually configured to convertchemical energy into electricity; providing a first terminal coupledwith the fuel cells; providing a second terminal coupled with the fuelcells; supplying fuel to the fuel cells; and controlling the supplyingusing a control system.
 210. The method according to claim 209 whereinthe controlling comprises controlling using the control systemcomprising a plurality of distributed controllers.
 211. The methodaccording to claim 209 wherein the providing the fuel cells comprisesproviding a plurality of polymer electrolyte membrane fuel cells. 212.The method according to claim 209 further comprising deactivating atleast one of the fuel cells.
 213. The method according to claim 212further comprising providing electricity to a load coupled with theterminals with the at least one fuel cell deactivated.
 214. The methodaccording to claim 209 wherein the supplying comprises supplying using amain valve.
 215. The method according to claim 209 wherein the supplyingcomprises: supplying using a main valve; and supplying using a pluralityof auxiliary valves.
 216. The method according to claim 215 wherein thecontrolling comprises controlling the main valve and the auxiliaryvalves using the control system.
 217. A method of controlling a fuelcell power system comprising: providing at least one fuel cellconfigured to convert chemical energy into electricity; providing afirst terminal coupled with the at least one fuel cell; providing asecond terminal coupled with the at least one fuel cell; supplying fuelto the at least one fuel cell; and monitoring for the presence of fuelwithin a housing about the at least one fuel cell using a controlsystem.
 218. The method according to claim 217 wherein the controllingcomprises controlling using the control system comprising a plurality ofdistributed controllers.
 219. The method according to claim 217 whereinthe providing the at least one fuel cell comprises providing the fuelcell having a plurality of polymer electrolyte membrane fuel cells. 220.The method according to claim 217 wherein the providing the at least onefuel cell comprises providing a plurality of fuel cells.
 221. The methodaccording to claim 210 further comprising deactivating at least one ofthe fuel cells.
 222. The method according to claim 221 furthercomprising providing electricity to a load coupled with the terminalswith the at least one fuel cell deactivated.
 223. The method accordingto claim 217 further comprising: coupling an operator interface with thecontrol system; and controlling the operator interface using the controlsystem to indicate the presence of fuel within the housing.
 224. Themethod according to claim 217 further comprising: selectively ceasingthe supplying responsive to the monitoring; and controlling the ceasingusing the control system.
 225. The method according to claim 217 whereinthe monitoring comprises monitoring using a fuel sensor.
 226. The methodaccording to claim 225 further comprising heating the fuel sensor. 227.A method of controlling a fuel cell power system comprising: providingat least one fuel cell configured to convert chemical energy intoelectricity; providing a first terminal coupled with the at least onefuel cell; providing a second terminal coupled with the at least onefuel cell; and monitoring a temperature within a housing about the atleast one fuel cell using a control system.
 228. The method according toclaim 227 wherein the controlling comprises controlling using thecontrol system comprising a plurality of distributed controllers. 229.The method according to claim 227 wherein the providing the at least onefuel cell comprises providing the fuel cell having a plurality ofpolymer electrolyte membrane fuel cells.
 230. The method according toclaim 227 wherein the providing the at least one fuel cell comprisesproviding a plurality of fuel cells.
 231. The method according to claim230 further comprising deactivating at least one of the fuel cells. 232.The method according to claim 231 further comprising providingelectricity to a load coupled with the terminals with the at least onefuel cell deactivated.
 233. The method according to claim 227 furthercomprising selectively one of increasing and decreasing the temperaturein the housing using an air temperature control assembly.
 234. Themethod according to claim 233 further comprising controlling the airtemperature control assembly using the control system and responsive tothe monitoring.
 235. The method according to claim 234 wherein thecontrolling comprises controlling to maintain the temperature in thehousing within a predefined range.
 236. The method according to claim234 wherein the controlling comprises controlling to maintain thetemperature in the housing within a predefined range of approximately25° Celsius and 8 ° Celsius.
 237. The method according to claim 227further comprising: directing air to the at least one fuel cell; andcontrolling the directing using the control system and responsive to themonitoring.
 238. The method according to claim 227 further comprising:inputting exterior air into the housing; and controlling the inputtingusing the control system and responsive to the monitoring.
 239. Themethod according to claim 227 further comprising monitoring atemperature exterior of the housing.
 240. The method according to claim227 wherein the monitoring comprises monitoring using a temperaturesensor.
 241. A method of controlling a fuel cell power systemcomprising: providing at least one fuel cell configured to convertchemical energy into electricity; providing a first terminal coupledwith the at least one fuel cell; providing a second terminal coupledwith the at least one fuel cell; shunting the at least one fuel cell;and controlling the shunting using a control system.
 242. The methodaccording to claim 241 wherein the controlling comprises controllingusing the control system comprising a plurality of distributedcontrollers.
 243. The method according to claim 241 wherein theproviding the at least one fuel cell comprises providing the fuel cellhaving a plurality of polymer electrolyte membrane fuel cells.
 244. Themethod according to claim 241 further comprising varying a period oftime of the shunting using the control system.
 245. The method accordingto claim 241 wherein the providing the at least one fuel cell comprisesproviding a plurality of fuel cells.
 246. The method according to claim245 further comprising deactivating at least one of the fuel cells. 247.The method according to claim 246 further comprising providingelectricity to a load coupled with the terminals with the at least onefuel cell deactivated.
 248. The method according to claim 245 furthercomprising sequentially shunting the fuel cells.
 249. The methodaccording to claim 245 further comprising shunting individual ones ofthe fuel cells.
 250. The method according to claim 245 furthercomprising shunting the fuel cells according to a specified order. 251.The method according to claim 245 further comprising: supplying fuel tothe fuel cells; and ceasing the supplying to shunted fuel cells.
 252. Amethod of controlling a fuel cell power system comprising: providing atleast one fuel cell configured to convert chemical energy intoelectricity; providing a first terminal coupled with the at least onefuel cell; providing a second terminal coupled with the at least onefuel cell; switching a connection immediate one of the terminals and theat least one fuel cell; and controlling the switching using a controlsystem.
 253. The method according to claim 252 wherein the controllingcomprises controlling using the control system comprising a plurality ofdistributed controllers.
 254. The method according to claim 252 whereinthe providing the at least one fuel cell comprises providing the fuelcell having a plurality of polymer electrolyte membrane fuel cells. 255.The method according to claim 252 wherein the providing the at least onefuel cell comprises providing a plurality of fuel cells.
 256. The methodaccording to claim 255 further comprising deactivating at least one ofthe fuel cells.
 257. The method according to claim 256 furthercomprising providing electricity to a load coupled with the terminalswith the at least one fuel cell deactivated.
 258. The method accordingto claim 252 further comprising monitoring a temperature within ahousing about the at least one fuel cell and the controlling isresponsive to the monitoring.
 259. A method of operating a fuel cellpower system comprising: initiating a start-up procedure; monitoring thetemperature within a housing containing at least one fuel cell;selectively adjusting the temperature within the housing using amodifying element responsive to the monitoring; and coupling a power buswith a terminal responsive to the monitoring.
 260. The method accordingto claim 259 further comprising monitoring for the presence of fuel.261. The method according to claim 259 further comprising: shunting theat least one fuel cell according to a duty cycle; and selectivelysetting the duty cycle to maximum.
 262. The method according to claim259 wherein the adjusting comprises heating using the modifying elementto increase the temperature.